Re: PCI DMA to small buffers on cache-incoherent arch

From: Tom Rini (
Date: Mon Jun 10 2002 - 12:29:09 EST

On Mon, Jun 10, 2002 at 07:22:26PM +0200, Oliver Neukum wrote:
> > > So is the consensus now that in general drivers should make sure any
> > > buffers passed to pci_map/unmap are aligned to SMP_CACHE_BYTES (and a
> > > multiple of SMP_CACHE_BYTES in size)? In other words if a driver uses
> > > an unaligned buffer it should be fixed unless we can prove (and
> > > document in a comment :) that it won't cause problems on an arch
> > > without cache coherency and with a writeback cache.
> >
> > And how about we don't call it SMP_CACHE_BYTES too? The processors
> > where this matters certainly aren't doing SMP...
> Definitely we should call it something different so we can limit it to
> architectures that need it.

No. We should just make it come out to a nop for arches that don't need
it. Otherwise we'll end up with ugly things like:

All over things like USB...

Tom Rini (TR1265)
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This archive was generated by hypermail 2b29 : Sat Jun 15 2002 - 22:00:18 EST